1. Field of the Invention
The present invention relates to a method and apparatus for varying the rate at which broadcast beacons are transmitted, and more particularly, for adaptively adjusting the rate of transmission in response to varying network conditions.
2. Related Art
In a wireless ad hoc network, all nodes of the network are equipped with wireless communications transceivers. Some of these nodes, commonly known as routers, are capable of network routing functions. Other of the nodes, commonly known as “endpoints,” are sources or destinations for data traffic.
Each node in an ad hoc network executes a set of algorithms and performs a set of networking protocols, which enable the nodes to locate other nodes. The networking protocols also enable the nodes to determine paths through the network for sending and receiving data traffic from source to destination. Additionally, the protocols enable the nodes to detect and repair ruptures in the network as nodes move, as nodes fail (i.e., leave the network), as battery power changes, as communications path characteristics change over time, and the like.
Certain types of wireless ad hoc networks employ beacons as a means by which network nodes can discover other nearby nodes. A beacon is a broadcast transmission that can be received by some or all of the nodes within transmission range. In some network schemes, all of the nodes in the network can broadcast beacons; in other networks, only a subset of the nodes can broadcast beacons.
Typically beacons contain information such as an identification of the node that is transmitting the beacon, forwarding error correction information, and other fields depending on the type of wireless networking protocols being employed in the ad hoc network.
Ad hoc wireless networks consisting of self-healing groups of network nodes typically transmit beacons at a fixed time interval or from a set of fixed time intervals. In some conventional networks, the intervals are “jittered” by adding a randomized offset to the fixed time interval to prevent system-wide synchronization of the beacon transmissions. While the jittering technique avoids network synchronization, it has limitations. For example, conventional networks with routers that transmit jittered beacon broadcasts are unable to selectively vary the rate of beacon transmission in response to varying network conditions and, thus, are unable to achieve maximum routing efficiency.